Fair Value Measurements (Summary Of Estimated Fair Values Of Significant Financial Instruments) (Detail) (USD $)	Sep. 30, 2014		Dec. 31, 2013
Fair Value Measurements [Line Items]
Valuation Allowance for Impairment of Recognized Servicing Assets, Balance	$ 11,000		$ 200,000
Unamortized premiums	43,000		61,000
Debt Instrument, Unamortized Discount	1,112,000	[1]	21,000	[1]
Hedge accounting adjustments			1,000,000
Fair Value, Measurements, Recurring [Member]
Fair Value Measurements [Line Items]
Securities held-to-maturity	2,873,886,000		3,106,931,000
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Measurements [Line Items]
Securities held-to-maturity	2,873,361,000		3,074,807,000
Federal Funds Purchased and Securities Loaned or Sold under Agreements to Repurchase, Fair Value Disclosure	1,257,595,000		1,365,427,000
Federal Home Loan Bank advances	2,301,591,000	[2]	2,063,312,000	[2]
Long-term debt	223,278,000	[3]	221,613,000	[3]
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Securities held-to-maturity [Member]
Fair Value Measurements [Line Items]
Securities held-to-maturity	3,699,825,000		3,370,912,000
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Deposits other than time deposits [Member]
Fair Value Measurements [Line Items]
Deposits	13,244,672,000		12,627,276,000
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Time deposits [Member]
Fair Value Measurements [Line Items]
Deposits	2,317,764,000		2,250,141,000
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Input (Level 3) [Member]
Fair Value Measurements [Line Items]
Securities held-to-maturity			28,490,000
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Input (Level 3) [Member] | Alternative investments (cost basis) [Member]
Fair Value Measurements [Line Items]
Other assets	19,208,000		17,047,000
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member]
Fair Value Measurements [Line Items]
Federal Funds Purchased and Securities Loaned or Sold under Agreements to Repurchase, Fair Value Disclosure	1,236,975,000		1,331,662,000
Federal Home Loan Bank advances	2,290,204,000	[2]	2,052,421,000	[2]
Long-term debt	226,208,000	[3]	228,365,000	[3]
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member] | Securities held-to-maturity [Member]
Fair Value Measurements [Line Items]
Securities held-to-maturity	3,641,979,000		3,358,721,000
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member] | Alternative investments (cost basis) [Member]
Fair Value Measurements [Line Items]
Other assets	16,188,000		16,582,000
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member] | Deposits other than time deposits [Member]
Fair Value Measurements [Line Items]
Deposits	13,244,672,000		12,627,276,000
Fair Value, Measurements, Recurring [Member] | Reported Value Measurement [Member] | Time deposits [Member]
Fair Value Measurements [Line Items]
Deposits	2,302,246,000		2,227,144,000
Fair Value, Measurements, Nonrecurring [Member] | Residential Mortgage [Member]
Fair Value Measurements [Line Items]
Mortgage servicing assets	19,651,000	[4]	20,983,000	[4]
Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Measurements [Line Items]
Loans held for sale	26,453,000		20,903,000
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Input (Level 3) [Member]
Fair Value Measurements [Line Items]
Loans and leases, net	13,377,939,000		12,515,714,000
Mortgage servicing assets	29,213,000	[4]	29,150,000	[4]
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member]
Fair Value Measurements [Line Items]
Loans held for sale	26,083,000		20,802,000
Loans and leases, net	$ 13,357,020,000		$ 12,547,203,000

[1] Related to senior fixed-rate notes due 2024 at September 30, 2014 and senior fixed-rate notes due 2014 at December 31, 2013

[2] The carrying amount of FHLB advances is net of $43 thousand and $61 thousand in hedge accounting adjustments and discounts at September 30, 2014 and December 31, 2013, respectively. The estimated fair value does not include such adjustments.

[3] The carrying amount of long-term debt is net of $1.1 million in discount at September 30, 2014 and $1.0 million in discount and hedge accounting adjustments, net at December 31, 2013. The estimated fair value does not include such adjustments.

[4] The carrying amount of mortgage servicing assets is net of $11 thousand and $0.2 million reserves at September 30, 2014 and December 31, 2013, respectively. The estimated fair value does not include such adjustments.